1. Field of the Invention
The present invention relates to a cooling fan for electric treadmill motor, and more particularly, to a cooling fan which prevents the armature of the treadmill motor from being burnt down due to being overheated.
2. Description of the Prior Art
First of all, referring to FIG. 2, two induced-draft fans 14, 16 are outwards disposed at two sides of a transmission shaft 12 the treadmill motor 10 respectively. When the treadmill motor 10 runs, the two induced-draft fans 14, 16 simultaneously perform the air draft operation. Moreover, a turning wheel 17 is coupled at the most outward side of the transmission shaft 12 so that a treadmill running belt (not shown) can be driven by a transmission belt 18.
Though this operation model seems reasonable and proper, the turning speed of the treadmill motor 10 is changeable in accordance with the user's operation so that the turning velocity varies tremendously (the adjustment range lies usually between at slowest 280 and at fastest 4800 revolutions) while the loading is kept at the same level (the weight of the user standing on the running belt of the treadmill). The two induced-draft fans 14, 16 are activated by the operation of the treadmill motor 10 so that the air draft efficiency increases when the treadmill motor 10 runs more rapidly; therefore, an optimal cooling effect can be achieved at this case. However, the air draft efficiency decreases when the treadmill motor 10 runs less rapidly and the treadmill motor 10 can be therefore burnt down due to being overheated as the expected cooling effect can't reached.
Briefly, when the revolution velocity of the treadmill motor 10 becomes slow and the loading keeps unchanged (that is, the weight of the user keeps unchanged), the induced-draft fan can't create an expected cooling effect, so that the life of the treadmill motor 10 of the prior art is often shortened.